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    <title>SNAP Data Processors - Algorithm Specification FLH/MCI</title>
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        <td class="header">&nbsp;
            FLH/MCI Algorithm Specification</td>
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<p>Algorithm Specification of the science processors of the MERIS/(A)ATSR Toolbox</p>

<h3>FLH/MCI</h3>

<p>
    The fluorescence line height and maximum chlorophyll index algorithms exploit the
    height of the measurement in a certain spectral band above a baseline, which passes
    through two other spectral bands. The best known algorithm is the fluorescence line
    height, where the phytoplankton chlorophyll fluorescence at 680.5 nm is measured and
    its height above a baseline through the measurements at 664nm and 708nm is calculated
    (see figure 1 below). This is used as an indicator for the biological activity of
    the phytoplankton. Also, other band combinations provide important indices,
    e.g. such as the maximum chlorophyll index (bands 680.5, 708 and 753nm, see
    figure 2), which can be applied, for example, to MERIS L1b measurements which
    can indicate red tides.
</p>

<p align="center">
    <img src="images/FLHFluorescence1.jpg"><br>
    Figure 1
</p>

<p>&nbsp;</p>

<p>The general form of a baseline algorithm is:</p>

<p><img src="images/FLHAlgorithm.gif"></p>

<p>
    where the indices 1 and 3 indicate the baseline bands and index 2 the peak wavelength.

    This algorithm is taken from the following publication:
    <object classid="java:org.netbeans.modules.javahelp.BrowserDisplayer">
        <param name="content" value="http://www.tandfonline.com/doi/abs/10.1080/014311699212470">
        <param name="text" value="Interpretation of the 685 nm peak in water-leaving radiance spectra in
        terms of fluorescence, absorption and scattering, and its observation
        by MERIS; J. F. R. Gower, R. Doerffer, G. A. Borstad,
        Int. J. Remote Sensing, 1999, vol. 20, no. 9, 1771-1786">
    </object>

<p>
    The algorithm implemented in the FLH/MCI processor contains an additional factor to
    correct the influence of thin clouds. This factor was introduced according to personal
    communications with J.F.R. Gower in February 2003.

<p align="center">
    <img src="images/FLH_2.gif"><br>
    Figure 2
</p>

<i>'If we use K=1, then FLH increases as radiance rises in thin cloud.
    We correct this using K=1.005. This is what I mean by "reducing the effect
    of thin cloud." We then find a mask at band 7 level 1 at about 50 radiance
    units gives a good picture. Using the same formula on level 2 reflectance
    data requires a mask at about .017 reflectance in band 7.'</i> , J.F.R. Gower.

<p>

<p align="center">
    <img src="images/FLHFluorescence2.jpg"><br>
    Figure 3
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